A paper-made packaging container capable of preserving drinks or fluidized foods such as milk, juice, and mineral water at the room temperature is obtained, for instance, from an outermost layer made of a thermoplastic material, a paper-made substrate layer, a conductive barrier layer (made of, for instance, aluminum foil), and a heat-sealable innermost layer.
A packaging container for a liquid food product has an opening for mounting thereon a lip from which the liquid food product is poured out or a cover, and a straw hole (opening) through which a straw is inserted, and the opening and the straw hole are provided at a vertex portion of the container. Furthermore a through hole as an opening is formed in the packaging container, and the opening is sealed with a barrier pull-tab from the outside and also with a patch film from the inside.
FIG. 2 illustrates two examples of a packaging container. An opening 22 from which a liquid food product is poured out is formed at a vertex portion of a container 21 shown in FIG. 2A, and a through hole 23 is formed in the laminated material for packaging, and an area including the through hole 23 is sealed by a paper-made substrate layer with an outermost layer made of a thermoplastic material, a conductive barrier layer, and a heat-sealable innermost layer laminated on both surfaces thereof.
FIG. 3 illustrates an example of an apparatus used for manufacturing a packaging container shown in FIG. 2.
In a filling machine shown in the example, a packaging material web 31 having thermoplastic material layers on both outer and inner layers of the paper-made substrate layer and wound up into a form like a roll is fed out and transferred by a roller in the filling machine; a through hole is provided by an pull-tab applicator 33 in the packaging material; the area is sealed with a barrier pull-tab from the outer side and with a batch fill from the inner side; the packaging material web is sterilized in a sterilizer bath 32; the packaging material is formed into a tube-like form with a forming roller 34; both end sides of the packaging material are overlaid on each other to form an overlap; the overlapped area is sealed with a longitudinal seal element 36 along the longitudinal direction of the tubular section; a liquid food product is filled into the tube from a filling pipe 35; this tube is fed downward by a length corresponding to one packaging container and is sealed in the transversal direction with a transversal sealing apparatus (not shown) to successively form pillow-like preliminarily formed bodies 37; the pillow-like preliminarily formed bodies linked to each other are separated to provide discrete preliminarily formed bodies by cutting a sealed zone between the adjoining preliminarily formed bodies at an intermediate point; and upper and lower flaps of the preliminarily formed body is bent with a finally forming machine 38 to provide a finally formed packaging container 39.
A container produced for preserving a quality of a paper-made packaging container is required to be inspected for such properties as the appearance, the sealing capability, and the capability of maintaining the fragrance. Because there is not the paper-made substrate layer in the opening and an undesirable condition for sealing may occur, it is especially desirable to inspect the sealing capability of the opening. There have been proposed various ideas for improvement of the sealing capability.
The ideas include, for instance, a seal inspection method enabling precise inspection of a sealed condition in a sealed section by energizing an aluminum foil layer inside a packaging material forming a paper-made container to measure an electrostatic capacitance (Refer to patent document 1), and a method in which flaps are peeled off from a wall of the container with the processing unit; a the container wall is cut with a sample preparing unit to prepare a sample; a sealing quality is inspected with a seal quality inspecting unit; a sealed zone is inspected with an image processor; and damages of the sealed zone are inspected with a seal damage inspecting unit (Refer to patent document 2).
With the conventional techniques as described above, however, it is required to break up a paper-made container for inspection, or to prepare a sample for inspection by cutting a container wall with a sample preparing unit. For the reasons described above, it is impossible to inspect all products on a production line.
[Patent document 1] Japanese Patent Laid-Open Publication No. 2005-326276
[Patent document 2] Japanese Patent Laid-Open Publication No. 2004-144503